1. Field of the Invention
The present invention relates generally to the field of aerodynamics, and more specifically, to a system of deployable control surfaces and an associated control system for effecting yaw, pitch and roll control of a vehicle. The system includes a plurality of deployable flaps whose respective centerlines are offset from the radius of the vehicle. Selective deployment of the flaps will result in a desired pitch, yaw and/or movement of the vehicle.
2. Description of the Related Art
Aerodynamic control systems for use in rocket launched projectiles are generally known. A particular control situation arises after the motor of a rocket or other such vehicle has fired, and the vehicle continues to move in what is commonly called a xe2x80x9ccoastingxe2x80x9d mode of operation. During vehicle coasting, there is a need for aerodynamic control to guide the vehicle.
Prior attempts to provide such a coasting guidance system have employed aero fins to achieve control during coast periods. The use of fins, however, can significantly reduce the number of missiles which can be packaged into a given cross section, such as the payload bay of an airplane or ship. Consequently, designs have been proposed which utilize flaps or panels which lie flush with the skin of the missile when not in use but which can be actuated to extend into the airstream to control the missile.
A significant disadvantage to the use of known flap designs is the difficulty of incorporating a design that effectively achieves roll control in addition to yaw and pitch control. Since most guided projectiles require some form of roll control, a system without roll control would likely require steering schemes, such as bank-to-turn, which require more time and therefore limit controllability.
In U.S. Pat. No. 5,398,887 to Wassom et al., a control system is disclosed for use with missiles and other projectiles. The control system provides pitch, roll and yaw control by actuating two (2) pairs of flaps disposed at the base of the projectile. Each flap is deployable on command by pivoting about a pivot axis disposed at the leading edge of the flap. The pivot axis is oriented at a first oblique angle to the radial plane of the projectile. Each flap is curved in a shape corresponding to the contour of the projectile body. The oblique angle of the pivot axis of one pair of flaps is opposite the oblique angle of the other pair of flaps.
The design of Wassom et al. has several disadvantages. First, the flaps are not of uniform design, which increases machining and manufacturing costs. Second, to obtain pure pitch or yaw control, the angles of the flaps must be paired in precise mirror images in order to avoid creating a roll force, which also increases machining and manufacturing costs. Finally, for hypersonic applications, the oblique hinging may create heating and/or mechanical interface problems and also adversely affect roll control.
U.S. Pat. No. 5,211,358 to Bagley describes a plurality of deployable fins which are moveable from a stowed position to a deployed position after launch by inflation of air bags. After launch, or after lowering of a launch platform in the case of aircraft, an actuator opens a valve supplying gas to inflate the bags. After the fin is locked into position, the airbag either rapidly deflates or is decoupled from the missile structure. The fins provide stabilization rather than pitch, roll or yaw control, however.
U.S. Pat. No. 5,975,461 to Ullrich discloses a vane control system for a guided missile, in which four vanes are disposed on the fuselage of the missile at a forward portion thereof. The vanes are deployable by actuation of a gear-and-motor arrangement whereby rotation of a gear causes the vanes to extend outwardly from a retracted position. As with the Bagley reference, the vanes appear to provide stabilization as opposed to pitch, roll and/or yaw control.
U.S. Pat. No. 5,564,652 to Trimbath describes a body spoiler for yaw control of a supersonic airplane. At the fore body of the fuselage, a plurality of spoilers are disposed, flush with the outer surface in a non-deployed position. The illustrated embodiment describes eight (8) spoilers arranged at equal radially spaced intervals. The patent describes deployment of the spoiler on the same side of the aircraft fuselage as a failed engine. The spoiler generates a shock wave which in turn produces pressure along the fore body thereby creating a yaw moment that substantially counterbalances the yaw moment generated by the malfunctioning engine. It is noted in the patent that a plurality of the radially disposed spoilers can be used to generate other forces, such as by deploying spoilers under the fuselage, an upward pitch movement is generated.
Although the aforementioned patents describe the use of control surfaces to achieve certain aerodynamic effects, a continuing need exists for a relatively simple structure for effecting pitch, yaw and/or roll movement in a vehicle.
It is an object of the present invention to provide an improved three axis flap control system.
It is a further object of the present invention to provide pitch, yaw, and roll control with a minimum number of parts and minimal infringement of packaging envelope.
It is a further object of the present invention to provide a control system that is variable to allow for a variety of vehicle loading conditions.
It is a further object of the present invention to minimize machining and manufacturing costs associated with a three axis flap control system.
The present invention provides a vehicle control system that provides pitch, yaw, and roll control. The control system includes a sensor, a controller, actuators, and four flaps. The flaps are positioned on the vehicle orthogonally, but offset from the vehicle centerline. By engaging various pairs of the flaps, any desired vehicle orientation may be achieved. The flaps are independently controlled. The flaps may be engaged to any desired angle of engagement, from none to the maximum possible.